Fuse unit



A. H. POWELL 2,386,060

FUSE UNIT Filef Oct. 29, 1942 2 Sheets-Sheet l Oct. 2, 1945. A POWELL 2,386,060

FUSE UNIT Filed Oct. 29. 1942 2 Sheets-Sheet 2 Inventor: Alrc H. Powell,

by /Vf JM/M1 His ttorneg.

Patented Oct. 2, 1945 FUSE UNIT Alric H. Powell, Yeadon, Pa., asslgnor to General Electric Company, a corporation of New York Application October 29, 1942, Serial No. 463,752

17 Claims.

My invention relates to fuse umts and more particularlyl to a dead front fuse unit which includes indicating means for indicating whether the fuse has operated.

Cartridge fuses are used to a large extent for protecting electric circuits of all sorts. They are used extensively in connection with control panels for electrical equipment. In such applications it is always desirable to reduce the panel space required therefor to a minimum and to provide a fuse unit which has a dead front so that there is no danger to operators at any time.

It is an object of my invention therefore, to provide a new and improved fuse unit which is attractive in appearance, requires less panel space than conventional fuse units used heretofore, which eliminates the requirement of a fuse block, and furthermore provides a dead front construction.

It is another object of my invention to provide an indicating type of fuse unit which is relatively inexpensive and which improves the interrupting capacity of the fuses used therewith.

Still another object of my invention is to provide a new and improved dead front indicating fuse unit which is provided with means which prevent shock or vibration from adversely affecting the unit.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will .be pointed out with particuiarity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawings in which Fig. l is a schematic diagram illustrating the electric circuit of the fuse unit of my invention; Fig. 2 is an exterior view of the fuse unit supported from a panel Fig. 3 is a top view of the fuse unit of Fig. 2 with the cover over the indicating lamp removed; Fig. 4 is a sectional view of the complete fuse unit taken on line 4 4 of Fig.l 3; Fig. 5 is a similar sectional view taken on line 5 5 of Fig. 3; Figs. 6 and '7 are partial views of the fuse unit in order to illustrate the locking features provided thereon, Fig. 8 is an exploded view of the conducting parts of the fuse unit; Fig. 9 is a view partly in section of a modification of the fuse unit of my invention; and Fig. 10 is an exploded view of a portion of the fuse unit of Fig. 9. i y

Referring now to the schematic diagram of Fig. 1 in which the corresponding parts thereof are designated by the same reference numerals as in the other figures of the drawings, I have illustrated the electrical circuit of the fuse unit generally indicated at Il which includes a conventional Cartridge fuse II having one terminal I2 thereof electrically connected to terminal I3 of the fuse unit. The upper terminal I 4 of the fuse is electrically connected by means of a conducting member I5 to be described in greater detail hereinafter to a conventional threaded shell I6 which in' turn is electrically connected to the other terminal Il of the fuse unit. As best shown in Fig. 8, the conducting shell I8 is very similar to the threaded shells used in connection with the ordinary, well-known lamp sockets. In order to indicate the operating condition of the fuse il', an indicating circuit is connected in parallel therewith which comprises a lamp schematically indicated at I8, serially connected with a resistor I8. Suitable conductors 20, 2| and 22 complete the circuit between the fuse II, lamp I8 and resistor I9. The general arrangement of the electrical circuit of Fig. 1 is well known and the resistor Il provides suillcient impedance in the indicator circuit including lamp I8 so that when fuse II is in the unblown condition, the current ilowing in the indicator circuit is insufficient to light lamp I8. However, upon rupture of fuse II the potential across the indicating circuit increases suiiiciently to cause lamp I8 to be lighted and readily indicate to the operator that replacement of fuse Il is necessary. My invention is particularly concerned with the new and improved fuse unit to be described hereinafter which incorporates the general features of the well-known indicating circuit schematically shown in Fig. 1 although certain portions of Fig. l have been illustrated in the preferred form embodying my invention.

The fuse unit embodying my invention as shown in Fig. 2 comprises a block or base of insulating material 23 which is provided` with ears 24 containing openings 25 therein by means of which lbase 23 may be suitably bolted or fastened to a panel, such as is indicated at 26, as by screws 21. Although in Figs. 2, 4, and 5 the fuse unit is indicated as mounted on a horizontal panel 28, it should be understood that as a practical matter this fuse unit would be mounted onga vertical panel for purposes which will become apparent hereinafter. The panel 28 is preferably a metal panel which would be grounded in a normal installation and insulating base 23 would therefore be mounted on the back of the panel which would have an opening 28 therein which cooperates with a recess 28 formed in insulating base 23.

At one end of insulating base 23 remote from panel 26 is provided a pair of terminals I3 and I1 .as indicated in Fig. l, the terminal I3 extending up through the center of insulating base 23 and terminating in a spring biased fuse contact 30 within recess 28. Fuse contact 30 is very similar in structure to the conventional center terminal found in the ordinary incandescent lamp socket. Terminal I1 on the other hand, enters base 23 at one side thereof and as best shown in Fig, 3, ex-

tends into a groove 29 which is an extension of recess 29. Terminal II is electrically connected to a washer 3| having an ear or extension 3|' which extends into groove 29. The shell I6 which is threaded in the manner of an ordinary lamp socket has a suitable cut-away portion indicated at 32 in Fig. 4 to permit insertion of washer 3| which has the extension 3|' thereof welded or otherwise fastened to terminal Il. The groove or recess extension 29 enables ready assembly of washer 3| and terminal II within the insulating base 23 which is constructed as a unitary structure of molded material or the like. Since terminal I3 extends through a central opening 33 in washer 3|, a suitable insulating washer 34 of mica or the like is interposed between Washer 3| and central spring contact 30. If desired, a suitable conducting washer 36 may be provided on the upper side of insulating washer 34. The assembly of the terminals I3 and I1 and the associated fuse terminals which comprise spring contact 30 and the conducting shell IB may readily be accomplished in the following manner. Washer 3| having an extension or ear 3| which is welded or otherwise suitably connected to terminal II is first inserted through the opening 32 in shell I9, after which this unit is put into position in recess 29 with the groove 29' permitting ready positioning of the conducting members. Thereafter insulating washer 34, conducting washer 36, and terminal I3 to which spring biased center contact 39 is electrically connected are moved into position. Terminals I3 and Il are suitably threaded so that they may be provided with lockwashers 31 and nuts 38, both for holding them in position on insulating base 23 as well as to enable external electrical connections to be made therewith which will be obvious from Figs. 2 and 4.

In addition to the insulating base and associated terminals described thus far, which serve as the fuse block and terminals and the like of the prior art arrangements, my new and improved fuse unit includes a removable insulating member 39 which includes a first or fuse receiving chamber 40 therein and a second chamber 4I spaced from the first chamber 40 for housing the leak resistor I9 and the lamp I8 described above. Insulating member 39 is generally cylindrical in construction and is adapted to fit into recess 29. The portion of insulating member 39 extending out of recess 29 is in eiect a manually operable knob. However, one end of insulating member 39 is somewhat reduced in diameter and is provided Wlth a. threaded portion including threads 42 for threadedly engaging the shell I6 to hold the insulating member 39 in the position indicated in Figs. 2, 4, and 5. The threaded portion to engage the terminal I4 of fuse II. The other end of conducting member I5 is provided with deformed ridges or corrugations I5" so that when conducting member I5 is in the position indicated in Figs. 4, 6, and 7 the end of conducting member I5 having the corrugations I5V fits into narrow slot 43. The corrugations or deformed ridges I5 are perpendicular to the long dimension of conducting member I5 so that as best shown in Fig. 7 they do not line up perfectly with the threads 42 on the threaded portion of insulating member 39. 'I'his misalignment of the deformed ridges or corrugations I5" of conducting member I5 with respect to the threads 42 of the threaded portion provides a suitable locking means to hold insulating member 39 in threaded engagement with shell IB so that shock and vibration will not cause its release. In additionas best shown in Figs. 4 and 6 the resiliency of conducting member I5 is such that the corrugated portion I5" tends to raise out of narrow slot or recess 43. However, when the insulating member 99 has the threaded portion 42 thereof engaged with threaded shell I6, the corrugated end of conducting member I5 is forced into slot 43 and consequently good contact between conducting member I5 and shell I8 is assured, partly due to the resilience of the conducting member I5 and partly due to the misalignment of the threads of the threaded portion 42 with the deformed ridges or corrugations I5". In addition, the forcing of the corrugated end of conductor I5 into narrow slot or recess 43 by virtue of the shape of conducting member I5 best shown in Fig. 8. causes the U-shaped end I5' to grip upper terminal I4 of fuse II, thereby providing an improved contact between terminal I4 of fuse II and shell I6 and consequently terminal I1 of fuse unit I9. It should be understood that although only one conducting member I5 has been shown, in certain applications where high currents are encountered, a plurality of such conducting members may be provided as is shown in Fig. 9-

I'he fuse receiving chamber 49 is so designed that when fuse II is inserted therein so asto have the terminal I4 thereof gripped by the U- shaped end I5' of conducting member I5 and the insulating member 39 is threadedly engaged with shell I6, the lower terminal I2 of the fuse is forced into intimate current conducting engagement with spring biased contact 30 oi insulating base 23.

The second or lamp receiving chamber 4I is accessible ,through removal of a cover 45 which is secured to the end of insulating member 99y opposite the threaded portion thereof. The cover 45 includes an opening 46 therein through which lamp I8 is readily discernible. .A suitable opening 41 is provided between fuse receiving chamber 40 and the chamber 4I through which electrical /connection between conducting member I5 and the indicating circuit is made. As illustrated in the drawings a suitable rivet 48 is fastened to the U-shaped end I5' of conducting member I5 and extends through opening 41 into the second chamber 4| wherein rivet 48 is electrically connected to conductor 29 which in turn is connected to one terminal of lamp I9.

In order to properly position lamp I9 in chamber 4I insulating member 39 is provided with raised portions 49 extending into chamber 4| which dene a suitable recess 50 therebetween of such size as to accommodate indicating lamp I8. Indicating lamp I9 is preferably a glow lamp of the type containing a mixture of inert gases such as a neon lamp or the like. Resistor I 9 is mounted on one of the raised portions 49 and has one end thereof electrically connected with the other terminal of lamp I8 as by conductor 2|, while the other terminal of resistor I9 is connected to conducting member 22 which extends down through insulating housing 39 through an elongated opening 5I therein and into fuse receiving chamber 40 so as to electrically engage terminal I2 oi fuse Il as indicated at i2' in Fig. 5.

Whenever the fuse II is in good current conducting condition a very low potential will be impressed across the parallel indicating circuit including lamp I8 and resistor I9 so that lamp I8 will not be lighted. On the other hand, as soon as the fusible element of fuse II is ruptured, the potential across the indicating circuit is .increased so that lamp I8 indicates to the operator through opening 46 that a new fuse is required.

With the arrangement described a dead iront construction is provided so that there is no danger to an operator that contact with a live circuit can be made. Furthermore, the condition of the fuse is clearly indicated lto the operator at all times. Also by virtue of the fact that the fuse Il is completely housed within base 23 of insulating member 29 the interrupting capacity thereof is considerably increased due to the smother- -ing action of the housing. A fuse, according to some standards is considered to satisfactorily interrupt a circuit if it is not blown apart in this process, and will not cause inflammable materialclosely adjacent thereto to ignite. It is obvious that with applicants improved arrangement therefore the interrupting capacity of the fuse units according to these standards is greatly increased with less dangerL to an operator due to flying fuse parts. The fuse may also be replaced without any danger to the operator merely by unscrewing insulatingrnernber 39 which then entirely disconnects the fuse from the associated electric circuit. In addition to the advantages enumerated above my new and irnproved fuse unit presents a pleasing appearance/ on a control panel as contrasted with the conventional fuse block used heretofore, and not only requires considerably less panel space as was mentioned above, but actually saves material. Furthermore, the locking feature described above makes this fuse unit especially desirable where it might be subjected to. shock and vibration.

When larger currents are to be carried by the fuse, it may be necessary to use cartridge fuses having greater external dimensions and accordingly the base and insulating member oi' the fuse unit must be increased in size and also the current conducting parts may require somewhat different construction. In Fig. 9 I have illustrated a fuse unit for accommodating a fuse for carrying and interrupting considerably large currents than the fuse of Fig. 4. The corresponding parts of Fig. 9 are designated by the same reference numerals as in Figs. 1 to 8. The base indicated at 23 is provided with an enlargement forming a contact chamber 52 below shell I6. In order to satisfactorily carry the larger currents the lower fuse contact illustrated generally at 53 comprises two multi-legged conducting members 5| each having an opening 55 therein to accommodate the screw which forms the center terminal I3 of the fuse unit I0. These multilegged members 54 are nested together with the legs of one member'out of alignment with the legs of the other so that effectively a single multilegged member having twice as many legs as each of the members 54 is produced. The legs of the contact engage lower fuse terminal I2 to produce a good electrical connection therebetween. With this construction a much more resilient Contact is provided with more legs or contact ngers which can be constructed of thinner material.

Shell i6 is larger in size than the corresponding member of Fig. 4 and as indicated in Fig. 9 is held in position by a washer 56 having bars or extensions 51 and 58. The extension 51 is electrically connected to the screw forming terminal I'I which also holds washer 56 in position. To further hold Washer 56 in postion a screw 59 passes through extension 58 and is threadedly engaged with a nut B0 embedded in a recess in base 23. Also in order to permit the escape of gases from the fuse chamber, I provide suitable openings BI in the base 23. These openings 6I vent the gases produced during circuit interruption and also provide ventilation during normal operation. They may also be pro-` vided in the fuse unit I0 of Fig. 2 if desired.

As was mentioned above in connection with Figs. 1 to 8, two conducting members I5 are provided in Fig. 9 only the ends having corrugations I5" being visible in the drawings. By using two such members larger currents can of course be carried and the locking feature is improved since two, locking members are correspondingly provided.

While I have shown and described certain particular embodiments of my invention, I do not desire my invention to be limited to the construction shown and described for it will of course be obvious that changes may be inade without departing from my invention. I, therefore, aim in the appended claims to cover all such` changes and modications as fall withinl the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fuse unit comprising a base of insulating material including a recess therein, a pair of terminals in said recess, one of said terminals comprising a threaded shell, an insulating member having a threaded portion for threadedly engaging said shell, said insulating member having .a fuse receiving chamber adapted to house a fuse therein, said insulating member being so constructed and arranged that when said fuse is in said chamber and said insulating member is threadedly engaged with said shell in said base that one end of said fuse is electrically connected with said other terminal, and means for electrically connecting the other end of said fuse with said shell, said last mentioned means serving to lock said insulating member and said fuse in position so that shock or vibration will not cause its release.

2. A fuse unit comprising a base of insulating material including a recess therein, a pair of terminals in said recess, one of said terminals cornprising a threaded shell, an insulating member having a threaded portion of insulating material for threadedly engaging said shell, said insulating member having a fuse receiving chamber, a fuse housed in said'chamber, said insulating member being so constructed and arranged that when said fuse is in said chamber and said insulating member is threadedly engaged with said shell in said base that one end of said fuse is electrically connected with said other terminal, means for electrically connecting the other end of said fuse with said shell, a second chamber in said insulating member, means mounted in said second chamber for indicating the blown condition of said fuse, and means for connecting said fuse across said terminals by rotating said insulating member.

said threaded portion so as to lock said insulating member in position against shock or vibration.

4. A fuse unit comprising a base of insulating material, a recess in said base, a pair of terminals mounted in said recess, one of said terminals comprising a threaded shell, an insulating member having a threaded portion forthreadedly engaging said shell, said threaded portion including a short discontinuous section, a fuse-receiving chamber in said insulating member, a fuse housed in said chamber, said insulating member being so constructedl and arranged that when said fuse is in said chamber and said insulating member is threadedly engaged with said shell in said base that one end oi said fuse is electrically connected with said other terminal, a conducting member for electrically connecting the other end of said fuse with said shell and having deformed ridges at one end thereof, the ridges on said conducting member being adapted to complete the discontinuous section of said threaded portion with said ridges somewhat out of alignment with the threads on said threaded shell so as to eiectively lock said insulating member and fuse in position against shock or vibration.

5. A fuse unit comprising a base of insulating material, a recess in said base, a pair of terminals mounted in said recess, one of said terminals comprising a threaded shell, an insulating member having a threaded portion for threadedly engaging said shell, a narrow slot in said insulating member transverse to the threads so as to form a discontinuous section of said threaded portion, said insulating member having a fuse-receiving chamber, a ruse housed in said chamber, said insulating member being so constructed and arranged that when said fuse is in 4said chamber and said insulating member is threadedly engaged with said shell in said base that one endoiv said fuse is electrically connected with said other terminal, and a conducting member for electrically connecting the other end 'of said fuse with said shell arranged to fit into said slot, one

end of said conducting member having corruga member transverse to the threads so as to form a discontinuous section of said threaded portion, and a conducting member i'or electrically connecting said shell with another member and arranged to t in said slot, one end of said conducting member having deformed ridges so that when said conducting member is in said slot said ridges end of said fuse with said other terminal.

assaoso complete the discontinuous section of said threaded portion with said ridges somewhat out of augment with the threads on said threaded portion so as to lock said insulating member in position against shock or vibration.

'7, A fuse unit comprising a base of insulating material, a recess in said base, a pair of terminals mounted in said recess, one'oi' said terminals comprising a threaded shell, an insulating member having a threaded portion for threadedly engaging said shell, a narrow slot in said insulating member transverse to said threads so as to form a discontinuous section of said threaded portion, said insulating member having a fuse-receiving chamber, a fuse housed in said chamber, said insulating member being so constructed and arranged that when'said fuse is in said chamber and said insulating member is threadedly engaged with said shell in said base that one end of said fuse is electrically connected with said other terminal, and a conducting member having a U- shaped end for electrically engaging the other end o! said fuse. the other end of said conducting member being adapted to fit into said slot, said conducting member having suilicient resilience to cause said other end thereof to raise out of said slot and electrically contact said shell when said insulating member is threadedly engaged with said shell and to be pressed into said slot so that said U-shaped end tightly grips said other end of said fuse.

8. A fuse unit comprising a base of insulating material including a recess therein, a pair of terminals in said recess, one of said terminals comprising a threaded shell, said other terminal comprising a resilient contact including a plurality of multi-legged conducting members nested together, an insulating member having a threaded portion for threadedly engaging said shell, said insulating member having a chamber adapted to house a fuse member so that when said insulating member is threadedly engaged with said shell in said base said fuse member has one end thereof in electrical engagement with said other terminal, and means for electrically connecting said other end of said fuse member with said shell, said last mentioned means being so constructed and arranged with respect to said insulating member and said shell to lock said insulating member in position so that shock and vibration will not cause its release.

9. A fuse unit comprising a base kof insulating material, a recess in said base, a pair of terminals mounted in said recess, one of said terminals comprising a resilient contact including a plurality of multi-legged conducting members nested together, an insulating member, means for mounting said insulating member in said recess, said insulating member having a fuse-receiving chamber adapted to receive a fuse, said insulating member being so constructed and arranged that when a fuse is housed in said chamber and said insulating member is mounted'in said recess in said base that one end of said fuse is electrically connected with said one terminaLand'a conducting member for electrically connecting the other 10. A fuse unit comprising a base o1 insulating material, a recess in said base, a pair of terminals mounted in said recess, one of said terminals comprising a resilient contact including a Vpair of multi-legged conducting members nested together with thev legs of one member axially displaced from the legs of the other member, an insulating member, means for mounting said insulating member in said recess, said insulating member having a fuse-receiving chamber adaptedl to receive a fuse, said insulating member being so constructed and arranged that when a fuse is housed in said chamber and said insulating member is mounted in said recess in said base that one end of said fuse is electrically connected with said one terminal, and a conducting member for electrically connecting the other end of said fuse with said other terminal.

l1. A fuse unit comprising a base of insulating material, a recess in said base, a pair of termi nals mounted in said recess, an insulating member, threaded means for mounting said insulating member in said recess, said insulating member having a fusereceiving chamber adapted to receive a fuse, said insulating member being so constructed and arranged that when a fuse is housed in said chamber and said insulating member is mounted in said recess in said base that one end of said fuse is electrically connected with one of said terminals, a conducting member for electrically connecting the other end of said fuse with said other terminal, means for indicating the blown condition of said fuse, comprising an indicating circuit including a lamp and serially arranged resistor, a second chamber in said insulating member for housing said lamp and resistor, and means including said rst mentioned means for locking said insulating member in position in said base so that shock and vibration will not cause its release.

12. A dead front cartridge fuse holder and indicator for the cartridge fuse held therein comprising in combination a panel board, a block having a recess therein secured to one face of said panel board, a pair of contact terminals loading into said recess in said block, a cartridge fuse retainer for removably retaining the cartridge fuse thereof within the recess of said block and in series with said contact terminals, a lamp for indicating rupture of the cartridge fuse, said lamp at times being Visible from the opposite side of said panel board from that to which said block is secured, a leak resistor in series with the terminals of said lamp, and means for connecting said lamp and leak resistor in series with said contact terminals, but in parallel with the cartridge fuse when retained in contact with said contact terminals.

13. A dead front fuse holder and indicator for the fuse held therein comprising in combination a panel board having an opening therein, a block having a recess therein secured to one side of said panel board, a pair of contact terminals connected to said block, a fuse retainer insertable through the opening within said panel board and removably seated within the recess of said block, one end of said fuse retainer projecting from the opposite side of said panel board from that t which said block is` secured when seated within the recess of said block, means for connecting the fuse in series with said contact terminals when the fuse retainer is inserted within the recess of said block, a lamp for indicating rupture of the fuse and visible at times from the projected end of said fuse retainer, a leak resistor connectedin series with the terminals of said lamp, said lamp and leak resistor being arranged in parallel with the fuse and in series with said contact terminals.

14. A dead front fuse holder and indicator for the fuse held therein comprising in combination a panel board having an opening therein, a block having a recess therein, a pair of contact terminals leading within the recess of said block, means for attaching said block to one face of said panel board, a fuse retainer insertable through the opening within said panel board for retaining the fuse thereof within the recess of said block and in series with said contact terminals, one end of said fuse retainer projecting from the opposite face of said panel board to which said block is attached when the fuse thereof is retained in series with said contact terminals, a lamp and leak resistor connected in series and arranged within the projected end of said fuse retainer whereby the lamp may at times be visible from said projected end of said fuse retainer and means for detachably connecting said lamp and resistor in series with said contact terminals but in parallel with the fuse when the latter is retained in series with said contact terminals.

15. Al dead front fuse holder and indicator for the fuse held therein comprising in combination a block having a recess therein, a pair of contact terminals extending within the recess of said block, a fuse retainer, a knob whereby said fuse retainer may be manually inserted within the recess of said block for retaining the fuse thereof in series with said contact terminals, a lamp for indicating the rupture of the fuse mounted within said knob and visible at times therefrom, a leak resistor connected in series with the terminals of said lamp, conductors carried by said fuse retainer and connectedin series with said lamp and leak resistor and a detachable connection between said conductors and said contact terminals whereby said lamp and leak resistor may be connected in series with said contact terminals and in parallel to the fuse when the fuse retainer is inserted within lthe recess of said block. v

16. A fuse unit comprising a base of insulating material for retaining a cartridge fuse, a pair of contact terminals supported by said base, a manually operable knob, a lamp for indicating rupture of the cartridge fuse mounted within said knob and visible at times from said knob, a leak resistor in series with the terminals of said lamp, contact members controllable by said knob and means whereby when said knob is in one position said contact members will cause the cartridge fuse lamp and leak resistor to be electrically connected in series with said contact terminals, but the lamp and leak resistor in parallel with the cartridge fuse.

-17. A dead front cartridge fuse holder and indicator for the cartridge fuse held thereby comprising in combination a panel board, a block secured to one faceof said Panel bOaId a Dil' of contact terminals carried by said block, a cartridge fuse removably retained within said block and in series with said contact terminals, a knob extending from the opposite face of said panel board, a lamp for indicating rupture of the cartridge fuse mounted within said knob, said lamp being at times visible from the opposite side of said panel board from that to which said block is secured, a leak resistor in series with the terminals of said lamp, and means for connecting said lamp and leak resistor in series with said contact terminals, butin parallel with the cartridge fuse when retained in contact with said Contact terminals.

ALRIC H. POWELL. 

